What are some use cases for the singlar ray output?
I still have not spent the time to do a proper write up of this, but here is a preview of the effect, and the Blend File for your own use. 

Even though this seemingly begins to look like a distance based thing, I really believe (in my own opinion, without further study) that this is still using amount of refraction as the basis for this effect, and the margin is pretty small. I would imagine that playing with settings such as the ones found here: This Link would change this potential up quite a bit, how ever I can see some sequential lighting animation being done with this node, as long as each light would have to pass through something that would cause this type of refraction like the glass prism shown in this answer.